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Crystals
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III-Nitride Materials: Properties, Growth, and Applications
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III-Nitride Materials: Properties, Growth, and Applications

A special issue of Crystals (ISSN 2073-4352). This special issue belongs to the section "Inorganic Crystalline Materials".

Deadline for manuscript submissions: closed (10 April 2024) | Viewed by 30017

Printed Edition Available!
A printed edition of this Special Issue is available here.

Special Issue Editors

Dr. Yangfeng Li

E-Mail Website
Guest Editor
College of Semiconductors (College of Integrated Circuits), Hunan University, Changsha 410082, China
Interests: GaN MOCVD epitaxy; InGaN LEDs; GaN HEMTs; micro-disk lasers; micro-LED displays
Special Issues, Collections and Topics in MDPI journals
Dr. Zeyu Liu

E-Mail Website
Guest Editor
School of Physics and Electronics, Hunan University, Changsha, Hunan 410082, China
Interests: thermal properties of GaN; thermal management of GaN devices
Dr. Mingzeng Peng

E-Mail Website
Guest Editor
School of Mathematics and Physics, University of Science and Technology Beijing, Beijing 100083, China
Interests: wide-bandgap semiconductors; 2D semiconductors; optoelectronics; GaN HEMT; power devices and physics
Prof. Dr. Yang Wang

E-Mail Website
Guest Editor
Songshan Lake Materials Laboratory, Dongguan 523808, China
Interests: III-V compound semiconductors; GaN-based materials epitaxy; GaAs-based materials epitaxy; micro-nano fabrication; MEMS
Dr. Yang Jiang

E-Mail Website
Guest Editor
Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Interests: GaN MOCVD epitaxy; InGaN LEDs; GaN HEMTs; solar cells; detectors
Dr. Yuanpeng Wu

E-Mail Website
Guest Editor
Department of Electrical Engineering and Computer Science, University of Michigan, Ann Arbor, MI 48109, USA
Interests: wide bandgap semiconductor; low-dimensional nanostructures; epitaxial growth; nanoelectronics; optoelectronic devices
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

III-Nitrides have been widely developed and researched in the past 30 years. The gallium nitride (GaN)-based light emitting diodes (LEDs) prevail in lighting, display, light communication, sterilization, etc. The GaN-based high electron mobility transistors (HEMTs) have already shown tremendous potential for high-frequency communications and power conversions. Compared to blue and green LEDs, GaN-based yellow or red LEDs and ultraviolet LEDs are deficient in high external quantum efficiency. The relatively high defects in the epilayers and the interface traps hinder the experimental performance of GaN HEMTs (e.g., breakdown voltage, Vth hysteresis, high dynamic Ron, etc.). The p-channel field effect transistor of GaN is still under-investigated. Compared to the incumbent Ga-polar counterpart, N-polar GaN demonstrates some intrinsic merits for both LEDs and HEMTs. Therefore, studies of N-polar GaN are also flourishing. As for GaN growth, metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), and hydride vapor phase epitaxy (HVPE) are the major methods. The growth kinetics of GaN remain to be clarified, especially on foreign substrates (e.g., sapphire, silicon, silicon carbide, etc.). Many open questions regarding III-Nitrides await the consensus of researchers.

This Special Issue of Crystals serves to provide a platform for researchers to report their results and findings in III-Nitrides materials, including growth, characterisations, structure designs, device fabrication procedures, optical and electronic properties, and their applications in emerging lighting, display, RF, power electronics systems, etc.

Potential topics include, but are not limited to:

  • The growth of III-Nitrides;
  • Deep insight into the growth mechanisms and device performance;
  • Novel structures of III-Nitrides devices;
  • Materials, optical, and electronic characteristics of III-Nitrides devices;
  • InGaN long wavelength LEDs;
  • GaN-based UV LEDs;
  • GaN-based micro-LED displays;
  • GaN-based lasers;
  • GaN HEMTs.

Dr. Yangfeng Li
Dr. Zeyu Liu
Dr. Mingzeng Peng
Prof. Dr. Yang Wang
Dr. Yang Jiang
Dr. Yuanpeng Wu
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Crystals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2100 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • InGaN LEDs
  • InGaN lasers
  • UV LEDs
  • HEMTs
  • growth
  • properties

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Published Papers (13 papers)

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Editorial

Jump to: Research, Review

7 pages, 213 KiB  
Editorial
III-Nitride Materials: Properties, Growth, and Applications
by Yangfeng Li
Crystals 2024, 14(5), 390; https://doi.org/10.3390/cryst14050390 - 23 Apr 2024
Cited by 1 | Viewed by 953
Abstract
Since the activation of magnesium (Mg) in p-type gallium nitride (GaN) [...] Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)

Research

Jump to: Editorial, Review

13 pages, 4417 KiB  
Article
Study on the Influence of KOH Wet Treatment on Red μLEDs
by Shuhan Zhang, Qian Fan, Xianfeng Ni, Li Tao and Xing Gu
Crystals 2023, 13(12), 1611; https://doi.org/10.3390/cryst13121611 - 21 Nov 2023
Cited by 1 | Viewed by 1424
Abstract
InGaN-based red micro-light-emitting diodes (µLEDs) of different sizes were prepared in this work. The red GaN epilayers were grown on 4-inch sapphire substrates through metal-organic chemical vapor deposition (MOCVD). Etching, sidewall treatment, and p- and n-contact deposition were involved in the fabrication process. [...] Read more.
InGaN-based red micro-light-emitting diodes (µLEDs) of different sizes were prepared in this work. The red GaN epilayers were grown on 4-inch sapphire substrates through metal-organic chemical vapor deposition (MOCVD). Etching, sidewall treatment, and p- and n-contact deposition were involved in the fabrication process. Initially, the etching process would cause undesirable damage to the GaN sidewalls, which leads to an increase in leakage current. Hence, we employed KOH wet treatment to rectify the defects on the sidewalls and conducted a comparative and systematic analysis of electrical as well as optical properties. We observed that the µLEDs with a size of 5 µm exhibited a substantial leakage current, which was effectively mitigated by the application of KOH wet treatment. In terms of optical performance, the arrays with KOH demonstrated improved light output power (LOP). Additionally, while photoelectric performance exhibited a decline with increased current density, the devices treated with KOH consistently outperformed their counterparts in terms of optoelectronic efficiency. It is noteworthy that the optimized devices displayed enhanced photoelectric characteristics without significantly altering their original peak wavelength and FWHM. Our findings point to the elimination of surface non-radiative recombination by KOH wet treatment, thereby enhancing the performance of small-sized red µLEDs, which has significant potential in realizing full-color micro-displays in near-eye projection applications. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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9 pages, 3119 KiB  
Article
First Demonstration of Extrinsic C-Doped Semi-Insulating N-Polar GaN Using Propane Precursor Grown on Miscut Sapphire Substrate by MOCVD
by Swarnav Mukhopadhyay, Surjava Sanyal, Guangying Wang, Chirag Gupta and Shubhra S. Pasayat
Crystals 2023, 13(10), 1457; https://doi.org/10.3390/cryst13101457 - 1 Oct 2023
Cited by 1 | Viewed by 1379
Abstract
In this study, carbon-doped semi-insulating N-polar GaN on a sapphire substrate was prepared using a propane precursor. Controlling the deposition rate of N-polar GaN helped to improve the carbon incorporation efficiency, providing a semi-insulating behavior. The material quality and surface roughness of the [...] Read more.
In this study, carbon-doped semi-insulating N-polar GaN on a sapphire substrate was prepared using a propane precursor. Controlling the deposition rate of N-polar GaN helped to improve the carbon incorporation efficiency, providing a semi-insulating behavior. The material quality and surface roughness of the N-polar GaN improved with modified deposition conditions. C-doping using 1.8 mmol/min of propane gave an abrupt doping profile near the GaN/sapphire interface, which was useful for obtaining semi-insulating N-polar GaN grown on sapphire. This study shows that further development of the deposition process will allow for improved material quality and produce a state-of-the-art N-polar semi-insulating GaN layer. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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13 pages, 3510 KiB  
Article
Crack-Free High-Composition (>35%) Thick-Barrier (>30 nm) AlGaN/AlN/GaN High-Electron-Mobility Transistor on Sapphire with Low Sheet Resistance (<250 Ω/□)
by Swarnav Mukhopadhyay, Cheng Liu, Jiahao Chen, Md Tahmidul Alam, Surjava Sanyal, Ruixin Bai, Guangying Wang, Chirag Gupta and Shubhra S. Pasayat
Crystals 2023, 13(10), 1456; https://doi.org/10.3390/cryst13101456 - 30 Sep 2023
Cited by 1 | Viewed by 1444
Abstract
In this article, a high-composition (>35%) thick-barrier (>30 nm) AlGaN/AlN/GaN high-electron-mobility transistor (HEMT) structure grown on a sapphire substrate with ultra-low sheet resistivity (<250 Ω/□) is reported. The optimization of growth conditions, such as reduced deposition rate, and the thickness optimization of different [...] Read more.
In this article, a high-composition (>35%) thick-barrier (>30 nm) AlGaN/AlN/GaN high-electron-mobility transistor (HEMT) structure grown on a sapphire substrate with ultra-low sheet resistivity (<250 Ω/□) is reported. The optimization of growth conditions, such as reduced deposition rate, and the thickness optimization of different epitaxial layers allowed us to deposit a crack-free high-composition and thick AlGaN barrier layer HEMT structure. A significantly high two-dimensional electron gas (2DEG) density of 1.46 × 1013 cm−2 with a room-temperature mobility of 1710 cm2/V·s was obtained via Hall measurement using the Van der Pauw method. These state-of-the-art results show great potential for high-power Ga-polar HEMT design on sapphire substrates. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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11 pages, 4118 KiB  
Article
Structural, Surface, and Optical Properties of AlN Thin Films Grown on Different Substrates by PEALD
by Sanjie Liu, Yangfeng Li, Jiayou Tao, Ruifan Tang and Xinhe Zheng
Crystals 2023, 13(6), 910; https://doi.org/10.3390/cryst13060910 - 3 Jun 2023
Cited by 5 | Viewed by 3006
Abstract
Plasma-enhanced atomic layer deposition was employed to grow aluminum nitride (AlN) thin films on Si (100), Si (111), and c-plane sapphire substrates at 250 °C. Trimethylaluminum and Ar/N2/H2 plasma were utilized as Al and N precursors, respectively. The properties of [...] Read more.
Plasma-enhanced atomic layer deposition was employed to grow aluminum nitride (AlN) thin films on Si (100), Si (111), and c-plane sapphire substrates at 250 °C. Trimethylaluminum and Ar/N2/H2 plasma were utilized as Al and N precursors, respectively. The properties of AlN thin films grown on various substrates were comparatively analyzed. The investigation revealed that the as-grown AlN thin films exhibit a hexagonal wurtzite structure with preferred c-axis orientation and were polycrystalline, regardless of the substrates. The sharp AlN/substrate interfaces of the as-grown AlN are indicated by the clearly resolved Kiessig fringes measured through X-ray reflectivity. The surface morphology analysis indicated that the AlN grown on sapphire displays the largest crystal grain size and surface roughness value. Additionally, AlN/Si (100) shows the highest refractive index at a wavelength of 532 nm. Compared to AlN/sapphire, AlN/Si has a lower wavelength with an extinction coefficient of zero, indicating that AlN/Si has higher transmittance in the visible range. Overall, the study offers valuable insights into the properties of AlN thin films and their potential applications in optoelectronic devices, and provides a new technical idea for realizing high-quality AlN thin films with sharp AlN/substrate interfaces and smooth surfaces. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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8 pages, 1188 KiB  
Article
Analysis of Photo-Generated Carrier Escape in Multiple Quantum Wells
by Jiaping Guo, Weiye Liu, Ding Ding, Xinhui Tan, Wei Zhang, Lili Han, Zhaowei Wang, Weihua Gong, Jiyun Li, Ruizhan Zhai, Zhongqing Jia, Ziguang Ma, Chunhua Du, Haiqiang Jia and Xiansheng Tang
Crystals 2023, 13(5), 834; https://doi.org/10.3390/cryst13050834 - 17 May 2023
Cited by 1 | Viewed by 1587
Abstract
Recent experiments have shown that more than 85% of photo-generated carriers can escape from multiple quantum wells (MQWs) sandwiched between p-type and n-type layers (PIN). In this work, we quantitatively analyze the relationship between the energy of carriers and the height of potential [...] Read more.
Recent experiments have shown that more than 85% of photo-generated carriers can escape from multiple quantum wells (MQWs) sandwiched between p-type and n-type layers (PIN). In this work, we quantitatively analyze the relationship between the energy of carriers and the height of potential barriers to be crossed, based on the GaAs/InGaAs quantum well structure system, combined with the Heisenberg uncertainty principle. It was found that that the energy obtained by electrons from photons is just enough for them to escape, and it was found that the energy obtained by the hole is just enough for it to escape due to the extra energy calculated, based on the uncertainty principle. This extra energy is considered to come from photo-generated thermal energy. The differential reflection spectrum of the structure is then measured by pump–probe technology to verify the assumption. The experiment shows that the photo-generated carrier has a longer lifetime in its short circuit (SC) state, and thus it possesses a lower structure temperature than that in open circuit (OC). This can only explain a thermal energy reduction caused by the continuous carrier escape in SC state, indicating an extra thermal energy transferred to the escaping carriers. This study is of great significance to the design of new optoelectronic devices and can improve the theory of photo-generated carrier transports. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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12 pages, 2235 KiB  
Article
Normally-Off p-GaN Gate High-Electron-Mobility Transistors with the Air-Bridge Source-Connection Fabricated Using the Direct Laser Writing Grayscale Photolithography Technology
by Yujian Zhang, Guojian Ding, Fangzhou Wang, Ping Yu, Qi Feng, Cheng Yu, Junxian He, Xiaohui Wang, Wenjun Xu, Miao He, Yang Wang, Wanjun Chen, Haiqiang Jia and Hong Chen
Crystals 2023, 13(5), 815; https://doi.org/10.3390/cryst13050815 - 13 May 2023
Viewed by 2991
Abstract
In this work, we used the Direct Laser Writing Grayscale Photolithography technology to fabricate a normally-off p-GaN gate high-electron-mobility transistor with the air-bridge source-connection. The air-bridge source-connection was formed using the Direct Laser Writing Grayscale Photolithography, and it directly connected the two adjacent [...] Read more.
In this work, we used the Direct Laser Writing Grayscale Photolithography technology to fabricate a normally-off p-GaN gate high-electron-mobility transistor with the air-bridge source-connection. The air-bridge source-connection was formed using the Direct Laser Writing Grayscale Photolithography, and it directly connected the two adjacent sources and spanned the gate and drain of the multi-finger p-GaN gate device, which featured the advantages of stable self-support and large-span capabilities. Verified by the experiments, the fabricated air-bridge p-GaN gate devices utilizing the Direct Laser Writing Grayscale Photolithography presented an on-resistance of 36 Ω∙mm, a threshold voltage of 1.8 V, a maximum drain current of 240 mA/mm, and a breakdown voltage of 715 V. The results provide beneficial design guidance for realizing large gate-width p-GaN gate high-electron-mobility transistor devices. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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12 pages, 4252 KiB  
Article
Micro-Raman Spectroscopy Study of Vertical GaN Schottky Diode
by Atse Julien Eric N’Dohi, Camille Sonneville, Soufiane Saidi, Thi Huong Ngo, Philippe De Mierry, Eric Frayssinet, Yvon Cordier, Luong Viet Phung, Frédéric Morancho, Hassan Maher and Dominique Planson
Crystals 2023, 13(5), 713; https://doi.org/10.3390/cryst13050713 - 22 Apr 2023
Viewed by 1617
Abstract
In this work, the physical and the electrical properties of vertical GaN Schottky diodes were investigated. Cathodo-luminescence (CL), micro-Raman spectroscopy, SIMS, and current-voltage (I-V) measurements were performed to better understand the effects of physical parameters, for example structural defects and doping level inhomogeneity, [...] Read more.
In this work, the physical and the electrical properties of vertical GaN Schottky diodes were investigated. Cathodo-luminescence (CL), micro-Raman spectroscopy, SIMS, and current-voltage (I-V) measurements were performed to better understand the effects of physical parameters, for example structural defects and doping level inhomogeneity, on the diode electrical performances. Evidence of dislocations in the diode epilayer was spotted thanks to the CL measurements. Then, using 2D mappings of the E2h and A1 (LO) Raman modes, dislocations and other peculiar structural defects were observed. The I-V measurements of the diodes revealed a significant increase in the leakage current with applied reverse bias up to 200 V. The combination of physical and electrical characterization methods indicated that the electrical leakage in the reverse biased diodes seems more correlated with short range non-uniformities of the effective doping than with strain fluctuation induced by dislocations. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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12 pages, 4394 KiB  
Article
Polarization Modulation on Charge Transfer and Band Structures of GaN/MoS2 Polar Heterojunctions
by Feng Tian, Delin Kong, Peng Qiu, Heng Liu, Xiaoli Zhu, Huiyun Wei, Yimeng Song, Hong Chen, Xinhe Zheng and Mingzeng Peng
Crystals 2023, 13(4), 563; https://doi.org/10.3390/cryst13040563 - 25 Mar 2023
Cited by 1 | Viewed by 1614
Abstract
As important third-generation semiconductors, wurtzite III nitrides have strong spontaneous and piezoelectric polarization effects. They can be used to construct multifunctional polar heterojunctions or quantum structures with other emerging two-dimensional (2D) semiconductors. Here, we investigate the polarization effect of GaN on the interfacial [...] Read more.
As important third-generation semiconductors, wurtzite III nitrides have strong spontaneous and piezoelectric polarization effects. They can be used to construct multifunctional polar heterojunctions or quantum structures with other emerging two-dimensional (2D) semiconductors. Here, we investigate the polarization effect of GaN on the interfacial charge transfer and electronic properties of GaN/MoS2 polar heterojunctions by first-principles calculations. From the binding energy, the N-polarity GaN/MoS2 heterojunctions show stronger structural stability than the Ga-polarity counterparts. Both the Ga-polarity and N-polarity GaN/MoS2 polar heterojunctions have type-II energy band alignments, but with opposite directions of both the built-in electric field and interfacial charge transfer. In addition, their heterostructure types can be effectively modulated by applying in-plane biaxial strains on GaN/MoS2 polar heterojunctions, which can undergo energy band transitions from type II to type I. As a result, it provides a feasible solution for the structural design and integrated applications of hybrid 3D/2D polar heterojunctions in advanced electronics and optoelectronics. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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11 pages, 2237 KiB  
Article
Investigation into the MOCVD Growth and Optical Properties of InGaN/GaN Quantum Wells by Modulating NH3 Flux
by Zhenyu Chen, Feng Liang, Degang Zhao, Jing Yang, Ping Chen and Desheng Jiang
Crystals 2023, 13(1), 127; https://doi.org/10.3390/cryst13010127 - 10 Jan 2023
Cited by 3 | Viewed by 2255
Abstract
In this study, the surface morphology and luminescence characteristics of InGaN/GaN multiple quantum wells were studied by applying different flow rates of ammonia during MOCVD growth, and the best growth conditions of InGaN layers for green laser diodes were explored. Different emission peak [...] Read more.
In this study, the surface morphology and luminescence characteristics of InGaN/GaN multiple quantum wells were studied by applying different flow rates of ammonia during MOCVD growth, and the best growth conditions of InGaN layers for green laser diodes were explored. Different emission peak characteristics were observed in temperature-dependent photoluminescence (TDPL) examination, which showed significant structural changes in InGaN layers and in the appearance of composite structures of InGaN/GaN quantum wells and quantum-dot-like centers. It was shown that these changes are caused by several effects induced by ammonia, including both the promotion of indium corporation and corrosion from hydrogen caused by the decomposition of ammonia, as well as the decrease in the surface energy of InGaN dot-like centers. We carried out detailed research to determine ammonia’s mechanism of action during InGaN layer growth. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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9 pages, 1925 KiB  
Article
Maximizing the Light Extraction Efficiency for AlGaN-Based DUV-LEDs with Two Optimally Designed Surface Structures under the Guidance of PSO
by Zizheng Li, Huimin Lu, Jianping Wang, Yifan Zhu, Tongjun Yu and Yucheng Tian
Crystals 2022, 12(12), 1700; https://doi.org/10.3390/cryst12121700 - 24 Nov 2022
Viewed by 1662
Abstract
A novel method of utilizing an intelligent algorithm to guide the light extraction surface structure designing process for deep-ultraviolet light emitting diodes (DUV-LEDs) is proposed and investigated. Two kinds of surface structures based on the truncated pyramid array (TPA) and truncated cone array [...] Read more.
A novel method of utilizing an intelligent algorithm to guide the light extraction surface structure designing process for deep-ultraviolet light emitting diodes (DUV-LEDs) is proposed and investigated. Two kinds of surface structures based on the truncated pyramid array (TPA) and truncated cone array (TCA) are applied, which are expected to suppress the total internal reflection (TIR) effect and increase the light extraction efficiency (LEE). By addressing particle swarm optimization (PSO), the TPA and TCA microstructures constructed on the sapphire layer of the flip-chip DUV-LEDs are optimized. Compared to the conventional structure design method of parameter sweeping, this algorithm has much higher design efficiency and better optical properties. At the DUV wavelength of 280 nm, as a result, significant increases of 221% and 257% on the LEE are realized over the two forms of optimized surface structures. This approach provides another design path for DUV-LED light extraction structures. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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Review

Jump to: Editorial, Research

26 pages, 4599 KiB  
Review
Recent Research on Indium-Gallium-Nitride-Based Light-Emitting Diodes: Growth Conditions and External Quantum Efficiency
by Naveed Jafar, Jianliang Jiang, Heng Lu, Muhammad Qasim and Hengli Zhang
Crystals 2023, 13(12), 1623; https://doi.org/10.3390/cryst13121623 - 23 Nov 2023
Cited by 4 | Viewed by 2637
Abstract
The optimization of the synthesis of III-V compounds is a crucial subject in enhancing the external quantum efficiency of blue LEDs, laser diodes, quantum-dot solar cells, and other devices. There are several challenges in growing high-quality InGaN materials, including the lattice mismatch between [...] Read more.
The optimization of the synthesis of III-V compounds is a crucial subject in enhancing the external quantum efficiency of blue LEDs, laser diodes, quantum-dot solar cells, and other devices. There are several challenges in growing high-quality InGaN materials, including the lattice mismatch between GaN and InGaN causing stress and piezoelectric polarization, the relatively high vapor pressure of InN compared to GaN, and the low level of incorporation of indium in InGaN materials. Furthermore, carrier delocalization, Shockley–Read–Hall recombination, auger recombination, and electron leakage in InGaN light-emitting diodes (LEDs) are the main contributors to efficiency droop. The synthesis of high-quality III-V compounds can be achieved by optimizing growth parameters such as temperature, V/III ratios, growth rate, and pressure. By reducing the ammonia flow from 200 sccm to 50 sccm, increasing the growth rate from 0.1 to 1 m/h, and lowering the growth pressure from 250 to 150 Torr, the external quantum efficiency of III-V compounds can be improved at growth temperatures ranging from 800 °C to 500 °C. It is crucial to optimize the growth conditions to achieve high-quality materials. In addition, novel approaches such as adopting a microrod crystal structure, utilizing the piezo-phototronic effect, and depositing AlN/Al2O3 on top of the P-GaN and the electron-blocking layer can also contribute to improving the external quantum efficiency. The deposition of a multifunctional ultrathin layers of AlN/Al2O3 on top of the P-GaN can enhance the peak external quantum efficiency of InGaN blue LEDs by 29%, while the piezo-phototronic effect induced by a tensile strain of 2.04% results in a 183% increase in the relative electroluminescence intensity of the LEDs. This paper also discusses conventional and inverted p-i-n junction structures of LEDs. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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17 pages, 2636 KiB  
Review
Research Progress and Development Prospects of Enhanced GaN HEMTs
by Lili Han, Xiansheng Tang, Zhaowei Wang, Weihua Gong, Ruizhan Zhai, Zhongqing Jia and Wei Zhang
Crystals 2023, 13(6), 911; https://doi.org/10.3390/cryst13060911 - 4 Jun 2023
Cited by 7 | Viewed by 6041
Abstract
With the development of energy efficiency technologies such as 5G communication and electric vehicles, Si-based GaN microelectronics has entered a stage of rapid industrialization. As a new generation of microwave and millimeter wave devices, High Electron Mobility Transistors (HEMTs) show great advantages in [...] Read more.
With the development of energy efficiency technologies such as 5G communication and electric vehicles, Si-based GaN microelectronics has entered a stage of rapid industrialization. As a new generation of microwave and millimeter wave devices, High Electron Mobility Transistors (HEMTs) show great advantages in frequency, gain, and noise performance. With the continuous advancement of material growth technology, the epitaxial growth of semiconductor heterojunction can accurately control doping level, material thickness, and alloy composition. Consequently, HEMTs have been greatly improved from material structure to device structure. Device performance has also been significantly improved. In this paper, we briefly describe MOCVD growth technology and research progress of GaN HEMT epitaxial films, examine and compare the “state of the art” of enhanced HEMT devices, analyze the reliability and CMOS compatibility of GaN devices, and look to the future directions of possible development. Full article
(This article belongs to the Special Issue III-Nitride Materials: Properties, Growth, and Applications)
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